The invention relates to the field of semiconductor sensors, and in particular to a two-wire sensor.
A two-wire sensor includes a measuring sensor that measures a physical parameter such as for example temperature, pressure, or field strength of a magnetic field, and electronic components for processing the signals delivered by the measuring sensor. Both the power supply and the conducting of the measured and processed measurement signals use only two lines, accounting for the name two-wire sensor. A two-wire sensor has only two terminals that simultaneously serve to supply current and conduct the measured and processed measurement signals.
Two-wire sensors may include contactless magnetic switches which, depending on the strength and direction of the magnetic field to be measured, provide a measurement signal whose current is indicative of field strength. The structural element is passive as seen from outside in the simplest case (the current/voltage characteristic can change in other ways as well if appropriate and its internal resistance changes). When a current is imposed, the voltage that can be tapped changes and when a voltage is impressed, the resultant current changes. Both (also in combination) can be evaluated as a signal on the receiver side. Such two-wire sensors are used for example in motor vehicles as belt buckle switches or position switches. When two-wire sensors are used in safety-relevant areas, high reliability is necessary. In particular, a defective or improperly operating two-wire sensor must be detected in a timely manner.
Therefore, there is a need for an improved two-wire sensor.